Magnetoresistance and de Haas-van Alphen Effect in YRu₂Si₂

We have measured the magnetoresistance and the de Haas-van Alphen effect of YRu₂Si₂. The Fermi surface and cyclotron mass of YRu₂Si₂ are compared to those of LaRu₂Si₂ and LaRu₂Ge₂. Main hole Fermi surfaces of the three compounds are similar and ellipsoidal in shape, which occupy about half of the Brillouin zone. The small hole Fermi surface with a shape of rugby ball is one in number for YRu₂Si₂, while three for LaRu₂Si₂ and LaRu₂Ge₂. A cylindrical Fermi surface and a multiply-connected Fermi surface exist for YRu₂Si₂, while there exists a doughnut like electron Fermi surface for LaRu₂Si₂ and LaRu₂Ge₂. The cyclotron masses of YRu₂Si₂ are about 50% and 10% larger than those of LaRu₂Si₂ and LaRu₂Ge₂, respectively.